Chiral liquid-crystalline elastomers bearing side-chain fluorinated groups and chiral crosslinking units

Chiral fluorinated side-chain liquid-crystalline elastomers (LCEs) IF - IVP were graft copolymerized by hydrosilylation reaction. The chemical structure, liquid-crystalline behavior and polarization property were characterized by use of various experimental techniques. The effective crosslink density of the chiral LCEs was studied by swelling experiments. All the samples IF - IVP displayed chiral smectic C mesophase (S-C*) on heating and cooling cycles. With increasing chiral crosslinking units in the elastomer systems, the glass transition temperature and chiral smectic C mesophase-isotropic phase transition temperature of fluorinated elastomers increased slightly, indicating that the temperature range of S-C* mesophase became narrow with increase of chiral crosslinking agents for all the chiral fluorinated elastomers. All the samples IF - IVP showed 0.12-0.16 mu C/cm(2) of spontaneous polarization.